(453e) Hybrid 3D Printing of Anisotropic Bottlebrush Polymer Nanocomposites

Introducing nanoparticles to polymer networks can significantly enhance the mechanical properties of the final parts, while simultaneously introducing new functionalities afforded by the nanoparticles. Printing polymer nanocomposites is mostly limited to extrusion-based techniques with low fidelity compared to light-based techniques, such as digital light processing (DLP). Moreover, the resins compatible with these techniques typically have low stretchability. It remains a challenge to DLP print nanocomposites at high nanoparticle loadings due to the increase in resin viscosity and reduction in optical opacity. Here, integrating direct ink write (DIW) and DLP, we develop a hybrid 3D printing platform that enables printing anisotropic bottlebrush polymer nanocomposites. We find this process to be highly efficient in orienting the anisotropic cellulose nanocrystals, while maintaining print fidelity comparable to conventional DLP printed parts. We further discuss the effects of extrusion parameters, extrusion patterns, and the curing process on the extent of alignment of cellulose nanocrystals and their subsequent effects on the mechanical properties of the nanocomposites through mechanical, optical and rheological measurements. Finally, we discuss the effects of using a newly developed stretchable bottlebrush polymer resin to enhance the stretchability of parts, while maintaining their stiffness, which is not possible through using conventional linear polymers. Our hybrid DIW-DLP process and bottlebrush polymer resin hold great potential in expanding the library of materials compatible with DLP to anisotropic polymer nanocomposites at high loadings.